Also, I am trying to update style.css from mod_community toolbar - but do not want to edit directly, tried placing it under socialize/html/mod_community_toolbar, but no luck
that because /modules/mod_community_toolbar/assets/css/style.css loaded after custom.css. for override that CSS:
1. goto joomla backend
2. goto template manager, and open socialize
3. click Custom Code section
4. Before </head>, put this value